The manufacturers of electrical equipment face a problem of making reliable connections between a thin flat conductive lead and conductive terminals or pads. The leads may, for example, be the conductors of a flexible printed circuit and/or may be the leads from flat pack integrated circuits, both of which may be required to be connected to flat pads on printed wiring boards. In the past, many arrangements have been used but perhaps the most frequently used arrangement has been to pre-coat both the lead and the pad with solder, place the flat lead against the pad and solder the joint. However, it has been found that such connections are subject to large proportion of failures, usually by the tendency of the leads to lift from the pad after soldering.
In the case of flexible circuits, another common practice has been to form enlarged terminals with through holes in a predetermined pattern at the end of the conductor. The cover coat, if present, is removed either in small areas around such terminals or over the entire area of the terminal. In either case, the terminals are then placed over corresponding pins in printed wiring pad and then soldered. This is an expensive arrangement and frequently there is a problem of delamination of the printed circuit in the vicinity of the terminal.
Another prior arrangement is to provide solderless connections by making the leads of a fairly hard alloy and forming them with protrusions or points. The protrusions are held against the conductive pad by a resilient member so that the protrusions are pressed into the pad. Most electronic components are manufactured with relaively soft leads and in order to use this arrangement, the component must be specially manufactured or modified after manufacture. Additionally, the assembly of such a circuit with the resilient member such as an elastomer is a time consuming and expensive process.
It is a general object of the present invention to provide an improved electrical connection and method of making it.
A more specific object is to provide an improved solder connection, and a method of making the same, between a thin, flat conductive lead and a flat conductive pad.